1. Field of the Invention
The present invention relates to redundant array of inexpensive disks (RAID) subsystems and to systems and methods for RAID striping.
2. Background Art
RAID disk subsystems are traditionally organized by associating a set of disk drives into a RAID group. U.S. Pat. No. 5,550,998 describes an existing RAID system. The RAID group is often viewed as a single logical unit. The capacities of disk drives have been increasing to such a size that operating systems or file systems may not utilize all of the space of such a RAID group. In an attempt to resolve this, some RAID products are capable of partitioning a bound drive set into multiple logical units.
In most cases, with this organization, the RAID subsystem requires all units to be homogeneous. In only a few cases, heterogeneous units with similar attributes can be combined into a RAID group. In general, these units must meet the lowest common denominator of capacity so as to have a consistent device relative address for RAID stripe allocation.
The one exception to this method of associating RAID groups is the HP AutoRAID, available from Hewlett-Packard Company, Palo Alto, Calif. In the HP AutoRAID, all drives compromise the basis to one of two RAID sets. There is one RAID 1 and one RAID 5 RAID set. Drives are partitioned into allocation units of the same size and space is allocated to either of the two RAID groups on request. Capacity is managed across all units to satisfy the RAID group requirement.
For the foregoing reasons, there is a need for an improved system and method for RAID striping that may accommodate heterogeneous units and that is more flexible than existing techniques for associating RAID groups.